The invention relates to that type of a screw fastener which is provided with a plastic patch for self-locking operation. Fasteners of this general type are disclosed for example in Villo Pat. 3,093,177 and Preziosi Pat. 3,294,139.
The present disclosure is particularly directed to the forming of a plastic patch on a fastener wherein the plastic material is of a character that makes an effective bond with the fastener if the fastener is preheated to a .[.temperatuer.]. .Iadd.temperature .Iaddend.high enough to melt an increment of plastic thereon. The molten plastic is shaped to the fastener and then the fastener is quenched to give the plastic the desired self-locking characteristic.
Employing plastic material of this capability makes it unnecessary to use a priming agent or any other expedient to cause the plastic to bond tenaciously to the fastener. This fact helps make possible the primary object of the invention which is to produce patch-type self-locking fasteners at a high production rate to make possible exceptionally low unit cost.